Thirteen cases of the Guillain-Barré syndrome are reviewed, all occurring with a similar relationship to recent commencement of treatment with the antidepressive drug zimeldine. The risk of developing Guillain-Barré syndrome was increased about 25-fold among patients receiving zimeldine, as compared with the natural incidence of the disorder. The cases described provide strong evidence that Guillain-Barré syndrome may occur as a specific, probably immunologically mediated, complication of drug therapy.